Are scandi grind edges weak?

[Daniel L]

Hi all,

There's been a lot of talk about how sharp scandinavian grinds are - mainly from the fact that the edge angles are so acute.

But does this sharpness come at the cost of weakening the edge compared to a traditionally ground knife?

I understand that laterally it's strong since the full thickness of the blade is actually quite low... but wouldn't the edge be easier to deform since it's so thin or am I missing something in the geometry?

Thanks,

 

[Cliff Stamp]

The edge angles are typically fairly acute, at around ten degrees per side, and yes this does make them weaker than an edge ground at a more obtuse angle. However depending on what you cut, ten degrees might be strong enough and thus the strength at higher angles does nothing productive and actually lowers cutting ability and edge retention, Mike Swaim did a lot of work along that line of thought. Many scandinavian blades come with initial hollow ground edges and these are really weak and will turn on even light wood work as the edge has almost no support and twists in woods readily. You need to flatten the edge first before the true performance was seen, Jim Aston was the first to note this in detail on line and discuss the large difference a full sharpening can make. Note Spyderco ships several of these blades with similar angles, the Calypso Jr. in ZDP-189 for example was as acute, many of their knives are under 15 degrees per side.

-Cliff

 

[kel_aa]

If you can stand 10 degrees per side at the very edge, then what do you need to rest of the blade thickness for?

I agree that the blade is stronger, that the geometry doesn't make much difference in very shallow cutting, and the lack of secondary grind makes some tasks easier (acting in the same way as a chisel/plane).

On strength, in what circumstances is the strength of a flat ground or saber blade not sufficient?

It takes a lot more work to maintain that Scandi grind compared to using a secondary grind. And if you start using a secondary grind, then you lose teh chisel/plane advantage.

 

[Cliff Stamp]

If you can stand 10 degrees per side at the very edge, then what do you need to rest of the blade thickness for?

Generally you don't, hence multi-beveling is more optimal, but much more expensive to make.

On strength, in what circumstances is the strength of a flat ground or saber blade not sufficient?

Generally flat ground blades can be far stronger because you can go with a thicker spine and still have the edge far thinner. Thus the blade is both stronger and cuts better and as you note is far faster to sharpen.

-Cliff

 

[kel_aa]

So then is the only appeal left the price and the fact that it is traditional in one region of the world? Would anyone like to have dental work done with a traditional bow drill?

I don't quite understand why Mr Ray Mears parades around the world with a thick Scandi costing hundreds of pounds. For that money, I would much prefer some extra minutes on the grinder.

 

[Cliff Stamp]

So then is the only appeal left the price and the fact that it is traditional in one region of the world?

The main reason is the idea has been promoted that the single bevel is responsible for the cutting performance when it is simply a matter of edge angle. When many people first use a Mora 2000 and compare it to a Cold Steel SRK they are quickly taught the "fact" that it is the single bevel which makes the Mora cut about twice as well (or more considering fatigue) on wood craft.

The first time I seriously used one I was really impressed, and like many who heavily promote that style I became interested in a custom version with better steel. That lasted until Wilson noted that if I wanted a bevel at ten degrees I could easily put one on any knife he made and with the edge at 0.005" thick it would easily outcut any knife with an edge 0.125" thick with the same angle and be far easier to sharpen.

He could have easily sold me a knife with that grind, but Wilson in general isn't very commercial in that respect.

For that money, I would much prefer some extra minutes on the grinder.

Generally, their main advantge is in the really low cost ones. You can get knives for about $5-$10 which don't have much competition in regards to full primary profiles in the same price range. The really expensive ones are kind of silly from a user point of view, it would be like paying the same price for a custom machete vs a knife with a primary profile of suitable taper. Fortunately the machete has not been promoted the same way though it is the exact same profile, flat stock with a single bevel edge.

-Cliff

 

[Daniel L]

Thansk Cliff - I have come to the same conclusions, with low cost versus performance being the primary attraction.

I couldn't quite uinderstand why users were so enamoured with custom versions in S30V when I thought they'd be better off with a more optimal (convex or just thinner in some cases) grind for the intended purpose.

 

[Jeff Clark]

The thing that caught my interest was inexpensive laminated steel blades. I got my first scandi grind knife mail order when I was 14. I forget whether it cost $2.00 or $4.00. It was a classic Mora knife named a "Norse King". They promoted the laminated blade as being extremely tough (you could bend it 90 degrees in a vice) while the edge was hard enough to pound through coins. All this was true yet it was a big disapointment to me. It did not cut better than thinly honed knives that I owned and it bent much easier than other knives. The outer steel layers were too soft for my taste. I had expected significant spring-back when you bent the blade, instead there was almost none.

 

[Cliff Stamp]

I couldn't quite uinderstand why users were so enamoured with custom versions in S30V when I thought they'd be better off with a more optimal (convex or just thinner in some cases) grind for the intended purpose.

Yes, that edge type is managable on the 1/16" blades and on easy to grind steels, on really thin blades like that you could also argue the benefit of a full grind is slim, but this doesn't hold if you compare what happens if you combine full grinds and thicker stock.

The outer steel layers were too soft for my taste. I had expected significant spring-back when you bent the blade, instead there was almost none.

The Japanese are similar with knives using mild steel for some laminates (not hardened at all), and even plain iron. Some of the saws are also similar and it is very easy to warp the blades, no spring at all in the spine support.

-Cliff

 

[Daniel L]

So it follows my conclusion about chisel ground edges - that their apparent "sharpness" is also due to the thinness and acuteness of the edge angle. There's no magical edge which has amazing slicing abilities as well as durability - the nearest being the convex edge.

 

[Cliff Stamp]

So it follows my conclusion about chisel ground edges - that their apparent "sharpness" is also due to the thinness and acuteness of the edge angle.

Yes, same thing, angle and thickness, if you tilt a v-ground bevel in hand it presents just like a chisel ground blade but does it get "sharper" because it was rotated. Chisel ground blades in general are just more acute than most v-ground bevels. Most people using convex edges in general are also using more acute angles and as well using much tougher steels, so you are usually comparing carbon vs stainless. Convex is essentially just many multi-bevels so is in general more optimal over v-ground than flat ground is over single bevel for the same reasons to a lesser extent.

-Cliff